Cognitive and affective mediators of altruism were investigated from a developmental perspective. Relations among children's social-inferential abilities, emotional arousal, and behavioral interventions in others' circumstances of distress were examined. Emotional arousal and prosocial interventions were measured in response to simulations of emotion. Assessments of perspective taking, role taking and prosocial moral reasoning were also made. Sixty children ages four to eleven were studied. Social-cognitive abilities and prosocial interventions frequently increased with age while levels of emotional arousal did not change with age. Controlling for age, both intelligence and affective arousal were predictors of prosocial interventions.